1. Field of the Invention
The present invention relates to the scanning operation of an optical scanner and, more specifically to a fluorescent color scanning method used in a scanner to accurately scan documents containing fluorescent substances.
2. Description of the Related Art
Following fast development of computer technology, the trend of office automation keeps going forward. To achieve office automation, it is necessary to scan paper documents into electronic files for transmission by E-mail through a network.
Because of the attractively bright-colored feature, fluorescent substance is intensively used in a variety of documents, for example, used in ink for color printer, paper, and fluorescent markers. However, because the radiance factor of regular commercialized fluorescence is over 1 under visible spectrum, it is difficult to accurately obtain the original fluorescent color by means of conventional scanning methods. FIG. 1 is a radiance factor-wavelength curve obtained from a salmon fluorescent substance under a standard light source A subject to CIE (Commission International de l'Eclairage). As illustrated, the radiance factor of the fluorescent substance is about 1.25 at wavelength 610 nm, which is much higher than the radiance factor of the reference substance of standard white used in scanners (i.e., whiteboard). Therefore, when scanning this salmon fluorescent substance with a scanner, a saturated phenomenon occurred at the photon received by the red color sensor, or at the converted signal, thereby causing a signal ratio distortion at the red color, green color and blue color sensors that control color tone and hue. Therefore, there are differences between the color tone and hue of the image scanned and the original document.